function isRunYear(year) {
    if (year % 4 == 0 && year % 100 !== 0 || year % 400 == 0) {
        alert(year + '是闰年');
    } else {
        alert(year + '是平年');
    }
    return year;
}
var re = isRunYear(prompt('输入您想查询的年份'));